ABB Relion 650 Series Applications Manual page 69

1MRK 505 287-UUS B
It should be remembered that the vectorial sum of the currents must be used (IEDs, Metrosil and
resistor currents are resistive). The current measurement is insensitive to DC component in fault
current to allow the use of only the AC components of the fault current in the above calculations.
The voltage dependent resistor (Metrosil) characteristic is shown in Figure 27.
A shunt can be added in parallel to the non-linear resistor in order to desensitize the function.
Series resistor thermal capacity
The series resistor is dimensioned for 200 W. Care shall be exercised while testing to ensure that if
current needs to be injected continuously or for a significant duration of time, check that the heat
dissipation in the series resistor does not exceed 200 W. Otherwise injection time shall be reduced
to the minimum.
The series resistor is dimensioned for 200 W. The condition: shall be fulfilled. In this condition the
continuous injection is allowed during testing.
Busbar protection REB650
Application manual
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Section 6
Differential protection
SEMOD54734-336 v6
63